Marshall first insisted during an interview with NFL Network that Cutler can be the MVP this season, and a few minutes later defended his belief, as well as the Bears quarterback.
Marshall said Cutler is different not only from when the two broke in together in Denver in 2006, but also from last season when they played in coach Marc Trestman's offense for the first time.
"It's night and day," Marshall said. "He's a totally different person, totally different athlete.
"He's the first one in the building, and that (stinks) because I try to be the first one in the building. He's there at, like, 5 a.m. He lives it. I think he has a great balance to his life now with his personal stuff."
Marshall sees Cutler not only as an MVP candidate, but developing into more of a leader - something Cutler has been criticized for in the past.
"I just think we're more efficient, he's leading us and it's a trickle-down effect," Marshall said. "From a leadership standpoint, he's bringing everyone along with him, he's making everyone better.
"As far as how efficient he is, it just makes our offense that much better and gives everyone confidence."
Trestman backed Marshall's statement about Cutler's improvement in his second year within the offense.
"He's able to get guys in the right position, change routes quickly and get the best and most out of each and every play," Trestman said. "That is kind of where he is. He is kind of fixing it at the line of scrimmage when he needs to get it done."
Cutler achieved a career-best passer rating of 89.2 last year, but has been known more for his big arm than victories or efficiency throughout his career.
Because of injuries, Cutler hasn't played a complete season since 2009, his first with the Bears.
Marshall said part of the reason he sees Cutler as MVP material is he has options in receivers including himself, Alshon Jeffery, running back Mart Forte and tight end Martellus Bennett, but also because of the offensive system, Trestman and offensive coordinator Aaron Kromer.
"It's not about me, it's not just about Matt or Jay, it's about the group," Marshall said.
Cutler and former backup Josh McCown led the Bears to second in the NFL in scoring last year, but the Bears were 5-6 in games Cutler started as the defense declined greatly due to age and injuries.
Cutler got better pass protection last season, and the Bears await the return of a key part of the offensive line.
Starting right guard Kyle Long has been cleared to return to practice on a limited basis after missing the first five practices due to a viral infection.
"He's got to get his legs back underneath him. I think by Saturday night you'll see him in pads," Trestman said.
Trestman said the 2013 first-round draft pick has some catching up to do.
"So he's missed out, no doubt about it, and we'll to accelerate the process as soon as he gets back in there," Trestman said.
NOTES: Eben Britton, who replaced Long at right guard in practice, suffered a left hamstring injury during pass rush drills Wednesday and is day to day. ... Jeffery returned to practice from a foot injury. ... Cornerback Tim Jennings is practicing on a limited basis after recovering from a quad injury suffered in the first practice.